This invention relates to a magnetic tape apparatus and, more particularly, to a magnetic tape apparatus having a reel brake mechanism.
FIG. 12 is a view of the main portion of a conventional magnetic tape apparatus. Reference numeral 1 is a taking-up reel winder of a taking-up reel gear and, 2 is a feed reel winder of a feed reel gear. Reference numberal 3 is a first reel brake arm on the take-up side with a first reel brake pad 3a on the take-up side for limiting the rotation of the taking-up reel winder 1, a first actuator pin 3b for actuating the first reel brake arm 3 on the taking-up side, and pivot shaft 3c about which the first reel brake arm 3 rotates. Numeral 4 is a second reel brake arm on the feed side with a second reel brake pad 4a on the feed side for limiting the rotation of the feed reel winder 2, a second actuator pin 4b for actuating the second reel brake arm 4 on the feed side, and a pivot shaft 4c about which the second reel brake arm 4 rotates. Numeral 1 is a plunger. 6 is a first lever for pressure-contacting the plunger. 7 is a second lever for holding the operation. 8 is a drive lever for changing the operation with a pivot shaft 8a about which the drive lever 8 rotates, an actuating pin 8b of the drive lever 8, and a drive pin 8c, 9 is a driving rotary cam for rotating the drive lever 8 about the pivot shaft 8a. 10 is a lower plate for controlling operation of the first and second reel brake arms 3 and 4 with a take-up side cam portion 10a formed for controlling the operation of the first reel brake arms 3, and a feed side cam portion 10b for controlling the operation of the second reel brake arm 4. 11 is an upper plate for controlling the first and the second reel brake arms 3 and 4 with a feed side cam portion 10b for controlling the second reel brake arm 4 formed on the upper plate 11.
FIG. 12 illustrates the brake mode upon the completion of the unloading or retrieval of the magnetic tape. FIG. 13 illustrates the brake mode upon the loading and unloading of a magnetic tape. FIG. 14 illustrates the brake mode upon the recording or reproducing of a magnetic tape, FIG. 15 illustrates the brake mode upon the quick feed of a magnetic tape. FIG. 16 illustrates the brake mode upon the instantaneous stoppage. The brake modes can be shifted by rotation of the drive lever 8 from that are progressively shown in FIGS. 12-14 during magnetic tape recording and reproducing, from that shown in FIG. 14 through 16 (instantaneous stoppage) during the tape quick feed, and that shown in FIG. 16.fwdarw.FIG. 13.fwdarw.FIG. 12 the magnetic tape take-up operation.
Next, the operation will now be described. FIG. 12 illustrates the reel brake mode in which the unloading of the magnetic tape has been completed and both the take-up reel winder 1 and the feed reel winder 2 are subjected to a braking force by the first and the second reel brake pads 3a and 4a. By rotating the drive pin 8c of the drive lever 8 in a clockwise direction using the rotary cam 9, the upper plate 11 shifts to the left. At this time, the lower plate 10 is prevented from moving to the left because its bent plate end face 10e engages against the pivot shaft 4c.
Therefore, the first and second actuating pins 3b and 4b are in a free state, and each reel brake arm 3 and 4 is pulled respectively by the first and the second springs 13 and 14 so that the first reel brake arm 3 is urged in a clockwise direction and the second reel brake arm 4 is urged in a counter-clockwise direction, and the take-up reel mount 1 and the feed reel mounts 2 are respectively engaged by the reel brake pads 3a and 4a.
FIG. 13 illustrates the reel brake mode upon loading of the magnetic tape. From the position shown in FIG. 12, the drive lever 8 is rotated in a counter clockwise by the rotation of the rotary cam 9. Therefore, the upper plate 11 is moved to the right by the elastic force of the third spring 17 connected at its left end to the upper plate 11 and at its right end to the lower plate 10 until the upper plate engages the drive pin 8c and stops. By the movement of the upper plate 11, the actuation pin 4b of the second reel brake arm 4 abuts against the feed side cam portion 11a and the counter-clockwise rotating motion of the second reel brake arm 4 is limited so that the second reel brake pad 4a and the feed reel winder 2 are slightly engaged. The first reel brake arm 3 is in the state similar to FIG. 12, and the brake force of the take-up reel winder 1 is supplied from the first spring 13. When this engagement force (brake torque) is expressed as T.sub.BL and, as shown in FIG. 9, when the feed side tape wound diameter is R.sub.A and the take-up side tape wound diameter is R.sub.S, then it is always necessary that the feed side brake engagement force (brake torque) T.sub.AL has a relationship of T.sub.AL /R.sub.A &lt;T.sub.BL /R.sub.S. This ensures that the magnetic tape for loading is delivered only from the side of the feed reel winder 2. When the loading magnetic tape is at the tape end condition illustrated in FIG. 10, the tape loading (pullingout) force F must satisfy a relationship F&lt;T.sub.2 =T.sub.BL /R.sub.max in order to pull out the tape from the reel on the shaft 21 while causing the slip of the brake on the reel on the shaft 21. That is, T.sub.BL must be made small in order to make the magnetic tape pulling force small. Considering digital audio tape (DAT) recorders for example, since R.sub.max =.phi.36.5 mm and R.sub.min =.phi.15 mm, R.sub.B /R.sub.A .sup.. T.sub.AL .apprxeq.2.5.sup.. T.sub.AL (max)&lt;T.sub.BL &lt;F.sup.. R.sub.max must be satisfied.
FIG. 14 illustrates the reel brake mode of the magnetic tape recording and reproducing states once the magnetic tape has been pulled out. The rotation of the rotary cam 9 causes a counter-clockwise rotation of the drive lever 8 to its limit. This causes the lower plate 10 which engages the drive pin 8c to move to the right. Therefore, the take-up side cam portion 10a and the feed side cam portion 10b lift the first and the second actuator pins 3b and 4b, the first and the second reel brake pads 3a and 4a disengage from the reel winders 1 and 2, whereby the reel winders 1 and 2 are brought into a freely rotatable state. At this time, the upper plate 11 is pulled by the third spring 17 and is urged to the right and stopped at a position where the stopper portion 11b abuts against the pivot shaft 3c. At the same time, a plunger pressing lever pressing pin 10c planted in the lower plate 10 is brought into a sliding contact with the cam portion 6a of the first lever 6, so that the first lever 6 which is for pressing the plunger rotates about the rotary central axis 23. At this time, since the engagement end 6b of the first lever 6 disengages from the bent portion 7a of the second lever 7 which is for pressing the plunger, the fourth tension spring 16 causes the second lever 7 to be urged and be rotated in counter-clockwise direction abutting the pivot central axis 23. The plunger contacting portion 7b of the rotated second lever 7 causes the movable iron core 5a of the plunger 5 to be actuated until it abuts against the iron core 5b disposed within the plunger holder.
FIG. 15 illustrates the reel brake mode in the magnetic tape rapid feed state. In the magnetic tape recording and reproducing state as shown in FIG. 14, the plunger 5 is energized and excited so that the movable iron core 5a is magnetically attracted and held and when the rotary cam 9 is rotated to rotate the drive lever 8 in the clockwise direction until immediately before the drive pin 8c abuts against the upper plate 11 of which stopper portion 11b is engaged and blocked by the pivot shaft 3c is shown in FIG. 15. By this operation, the tape quick feed state illustrated in FIG. 15 is realized. By the exciting of the plunger 5, the engagement pin 10d engages against the tip engaging portion 7c of the second lever 7 which is the engaged plunger pressing lever, so that the lower plate 10 is brought into the state where the first and the second reel brake arms 3 and 4 are not engaged with the first and the second reel winders 1 and 2.
FIG. 16 illustrates the reel brake mode in which the instantaneous stoppage from the magnetic tape quick feeding state shown in FIG. 15 has been completed. In the reel brake mode in the quick feeding state shown in FIG. 15, when the plunger 5 is deenergized, the second lever 7 is rotated clockwise by the tension of the fifth spring 15. By this rotation, the engagement portion 7c disengages from the engagement pin 10d, whereby the lower plate 10 is moved in the left-hand direction by the tension force of the third spring 17 until its bent end face 10e abuts and stops against the pivot shaft 4c. At this time, the first and the second actuation pins 3b and 4b disengage from the take-up side cam portion 10a and the feed side cam portion 10b to release the first and the second reel brake arms 3 and 4. The first reel brake arm 3 is rotated by the tension forced of the first spring 13 so that the first reel brake pad 3a engages against the take-up reel winder 1 to brake its rotation. The second reel brake arm 4 is rotated by the tension force of the second spring 14 so that the second reel brake pad 4a engages against the feed reel winder 2 to brake its rotation.
Next, the reel brake mode upon the magnetic tape unloading will be described. The feed reel winder 2, to which the second reel brake pad 4a is slightly engaged in the same mode as the reel brake mode upon the magnetic tape loading as shown in FIG. 13, is rotated in the counterclockwise direction by a power transmission mechanism (not shown) to take up the magnetic tape. The torque relationship at this time will now be discussed.
The take-up reel winder 1 shown in FIG. 13 is given a brake torque of T.sub.BUL (=T.sub.BL) in FIG. 10. When the winding torque at the time of taking up the tape of the feed reel winder 2 is T.sub.rAUL, then in order that the feed reel winder 2 takes up the magnetic tape without simultaneously rotating the take-up reel winder 1, a relationship Tr.sub.AUL /R.sub.min &lt;T.sub.BUL /R.sub.max (=T.sub.BL /R.sub.max) must be satisfied.
That is, Tr.sub.AUL &lt;R.sub.min /R.sub.max.sup.. T.sub.BL =0.4 T.sub.BL (for DAT min.) must be held. As understood from this, for an appropriate magnetic tape loading force F, T.sub.BL must be small, and for a small T.sub.BL, T.sub.rAUL must be further small.
The cassette pack discharge operation after unloading the magnetic tape is achieved after the shifted as shown in FIG. 13 to FIG. 12. During this shift, the first and the second reel brake arms 3 and 4 keep the taking up reel winder 1 and the feed reel winder 2 braked.
Since the conventional magnetic tape apparatus is constructed as above described, in order to keep the magnetic tape loading force small, the reel brake force must be small and the magnetic tape take-up torque upon the magnetic tape unloading torque must be even smaller. Thus when the taking-up torque is increased within the cassette half due to a magnetic tape winding disturbance, when the magnetic tape is released outwardly of the cassette half for any reason, and when the magnetic tape is disturbed by the magnetic tape being caught outside the cassette half, the magnetic tape cannot be unloaded or retrieved into the cassette due to an insufficient taking-up torque during unloading of the magnetic tape.
Also, when the winding torque upon the magnetic tape unloading is made large so that the magnetic tape can be taken up even when the magnetic tape is disturbed, the magnetic tape is pulled by the magnetic tape unloading side reel (A side) and the non-feeding side reel (B side) is forced to rotate, whereby the tape position before and after the unloading of the magnetic tape shifts and, when the tape is to be reproduced, the reproducing position is substantially shifted from the previous reproducing prior to the unloading of the magnetic tape.